Hydroisomerization of Benzene-Containing Gasoline Fraction on Pt/B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pt/WO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

The effect of the hydroisomerization conditions of the benzene-containing fraction of catalytic reforming gasoline on the yield and composition of products is studied on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts. These catalysts allow benzene to be completely removed from the raw material. At the same time, the greatest yields of liquid products are obtained with minimal losses of the octane number at 2 MPa, a mass feedstock hourly space velocity (MFHSV) of 2 h^?1, and 325°C: 96.3 and 95.4 wt % on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts, respectively. The activity of the catalysts is maintained for 100 h during their operation.     

Bimetallic Pd–Cu/ZnO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pd–Cu/ZrO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for methanol synthesis

Monometallic copper and bimetallic palladium-copper catalysts supported on ZnO–Al₂O₃ and ZrO₂–Al₂O₃ were prepared by conventional impregnation method and tested in methanol synthesis reaction under elevated pressure (3.5 MPa) in gradientless reactor at 220°C. The physicochemical properties of prepared catalytic systems were studied using BET, X-ray, TPR-H₂, TPD-NH₃ techniques. The promotion effect of palladium on catalytic activity and selectivity of copper supported catalyst in methanol synthesis reaction was proven. The highest activity of this system is explained by the Pd–Cu alloy formation.     

Comparison of Ti/BDD and Ti/SnO<Subscript>2</Subscript>–Sb<Subscript>2</Subscript>O<Subscript>5</Subscript> electrodes for pollutant oxidation

Anodic oxidation is a promising process for degrading toxic and biologically refractory organic pollutants present in wastewater treatment. Proper selection of electrodes is the key to reach effective and economic operation. In this study, two types of electrodes, i.e. the recently developed Ti/BDD and Ti/SnO₂–Sb₂O₅, which is generally believed to be superior to the conventional electrodes, were compared under the same conditions. It was found that the Ti/BDD electrode could mineralize both phenol and reactive dyes effectively. But the Ti/SnO₂–Sb₂O₅ electrode could only mineralize phenol. When oxidizing more refractory reactive dyes, it demonstrated very poor activity. In addition, the Ti/BDD electrode had a service life of 264 h in an accelerated life test, but the Ti/SnO₂–Sb₂O₅ was irreversibly damaged within several seconds. The direct experimental comparison in the present study indicates that the Ti/BDD electrode is much better than the Ti/SnO₂–Sb₂O₅ electrode for pollutant oxidation.     

Hydrodechlorination of CCl<Subscript>4</Subscript> on Pt–Au/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

A series of Pt/Al₂O₃ catalysts were prepared by the impregnation method and were characterized by TEM, XRD, H₂ and CO chemisorptions, and investigated in the hydrodechlorination of tetrachloromethane. Three Pt-rich, Pt–Au/Al₂O₃ catalysts (Pt₁₀₀, Pt₉₅Au₅ and Pt₉₀Au₁₀) showed a similar metal particle size (~2.5–2.7 nm), so observed changes in the catalytic behavior are ascribed to alloying effect, especially because a considerable degree of Pt–Au mixing was achieved in the bimetallic samples. It appeared that by introducing very small amount of gold (10 at.%) to platinum, the catalytic activity is increased. It is argued that the occurrence of this moderate synergistic effect is associated with a decreased tendency of surface chloriding when platinum is alloyed with gold. Zbigniew Kowalczyk—deceased.     

Role of CeO<Subscript>2</Subscript> in Rh/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for CO<Subscript>2</Subscript> Reforming of Methane

Abstract  

The Rh/α-Al₂O₃ catalyst was modified by CeO₂ in order to improve the thermal stability and the carbon deposition resistance during the CO₂ reforming of methane The carbon formation was determined by TPO, TEM and Raman spectroscopy. Characterization results showed that the incorporation of Ce in the support inhibits the carbon deposition, increasing the useful life and the stability of the Rh base catalysts.     

Conversion of 4-Methylanisole Catalyzed by Pt/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and by Pt/SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: Reaction Networks and Evidence of Oxygen Removal

Abstract  

The conversion of 4-methylanisole, a prototypical bio-oil compound, was catalyzed by Pt/Al₂O₃, Pt/SiO₂-Al₂O₃, or HY zeolite at 573 K and atmospheric pressure. More than a dozen products were formed with each catalyst, the most abundant being 4-methylphenol, 2,4-dimethylphenol, and 2,4,6-trimethylphenol; toluene was also a major product when the catalyst was supported platinum with H₂ as a co-reactant. 4-Methylphenol was the only methylphenol isomer formed in significant yields, which indicates that migration of the methyl group on the aromatic ring is not significant under the selected reaction conditions. The data determine approximate reaction networks including reactions forming 4-methylphenol, 2,4-dimethylphenol, and toluene as primary products. The kinetically significant reaction classes were transalkylation, observed with all three catalysts, and hydrogenolysis (including hydrodeoxygenation) and hydrogenation, observed only with the platinum-containing catalysts operating in the presence of H₂. Data such as those reported here provide a starting point for predicting the conversion of whole bio-oils for removal of oxygen and upgrading of fuel properties.     

Comparative Study on Nano-Sized 1 wt% Pt/Ce<Subscript>0.8</Subscript>Zr<Subscript>0.2</Subscript>O<Subscript>2</Subscript> and 1 wt% Pt/Ce<Subscript>0.2</Subscript>Zr<Subscript>0.8</Subscript>O<Subscript>2</Subscript> Catalysts for a Single Stage Water Gas Shift Reaction

Abstract  

A comparative study on nano-sized Pt/Ce_0.8Zr_0.2O₂ and Pt/Ce_0.2Zr_0.8O₂ catalysts in a single stage water gas shift (WGS) reaction was carried out. These catalysts were prepared by impregnating 1 wt% Pt on nano-sized cubic (Ce_0.8Zr_0.2O₂) and tetragonal (Ce_0.2Zr_0.8O₂) supports. Both catalysts have been applied to WGS under identical conditions to understand beneficial effect of cubic/tetragonal phases of Ce_(1 − x)Zr_(x)O₂. 1 wt% Pt/Ce_0.8Zr_0.2O₂ exhibited higher CO conversion than 1 wt% Pt/Ce_0.2Zr_0.8O₂. In addition, 1 wt% Pt/Ce_0.8Zr_0.2O₂ catalyst showed relatively stable activity with time on stream. The high activity/stability of 1 wt% Pt/Ce_0.8Zr_0.2O₂ catalyst was correlated to its higher Pt dispersion and easier reducibility.     

Effects of the geometry and operating temperature on the stability of Ti/IrO<Subscript>2</Subscript>–SnO<Subscript>2</Subscript>–Sb<Subscript>2</Subscript>O<Subscript>5</Subscript> electrodes for O<Subscript>2</Subscript> evolution

Ternary IrO₂–Sb₂O₅–SnO₂ anode has shown its superiorities over IrO₂ and many other electrocatalysts for O₂ evolution, in terms of electrochemical stability, activity and cost. The performance of IrO₂–Sb₂O₅–SnO₂ anodes is affected by its electrochemical properties and operating conditions. In this paper, the electrochemical stability and activity of the Ti/IrO₂–Sb₂O₅–SnO₂ anodes prepared with three different geometries were investigated under different operating conditions. It was found that anodes with large mean curvature have high electrochemical stability. Although increasing temperature results in a decrease in the stability of Ti/IrO₂–Sb₂O₅–SnO₂, the anode with a mean curvature of 200 m⁻¹ still shows acceptable service life even at 70 °C. This tolerance of high temperature was attributed to the thermal expansion difference between the substrate and the coating layer, the redox window for Ir(V)/Ir(IV) conversion, and the redox reversibility of Sb and Sn species in the coating layer.     

Novel Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> aerogel/porous zirconia composite with ultra-low thermal conductivity

Highly porous zirconia fibers networks with a quasi-layered microstructure were successfully fabricated using vacuum squeeze moulding. The effects of inorganic binder content on the microstructure, room-temperature thermal and mechanical properties of fibrous porous zirconia ceramics were systematically investigated. Al₂O₃–SiO₂ aerogel was impregnated into fibrous porous ceramics, and the microstructures, thermal and mechanical properties of Al₂O₃–SiO₂ aerogel/porous zirconia composites were also studied. Results show that the Al₂O₃–SiO₂ aerogel/porous zirconia composites exhibited higher compressive strength (i.e., 1.22 MPa in the z direction) and lower thermal conductivity [i.e., 0.049 W/(m/K)]. This method provides an efficient way to prepare high-temperature thermal insulation materials.     

Anodic oxidation of organic pollutants on a Ti/SnO<Subscript>2</Subscript>–Sb<Subscript>2</Subscript>O<Subscript>4</Subscript> anode

A Ti/SnO₂–Sb₂O₄ electrode was prepared by alternate Sn and Sb electrodepositions using the thermo-electrochemical method. The chemical, electrochemical, and structural characterization of the electrode was performed and it was tested in the anodic oxidation of several pollutants, phenol, ibuprofen, acid orange 7 (AO7), and diclofenac, all in aqueous 0.035 M Na₂SO₄ solutions at current densities of 10 and 20 mA cm⁻². After the 24 h assay, removal of chemical oxygen demand, total organic carbon (TOC) and absorbance were very high, especially at the higher current density. TOC removals presented the lowest value. However, after 24 h at 20 mA cm⁻², TOC removals were: phenol—94%; ibuprofen—83%; AO7—88%; and diclofenac—73%. Combustion efficiency and instantaneous and mineralization current efficiencies were also determined.     

Phase relationships in the Na<Subscript>2</Subscript>ZnP<Subscript>2</Subscript>O<Subscript>7</Subscript>–LiKZnP<Subscript>2</Subscript>O<Subscript>7</Subscript> system

The phase relationships in the Na₂ZnP₂O₇–LiKZnP₂O₇ system are studied. They are represented by a mixture of the starting components in the subsolidus region. The eutectic was found at a temperature of 640°C and composition of 0.5LiKZnP₂O₇. The phase formation of this system is compared with the previously studied NaKZnP₂O₇–LiKZnP₂O₇ system. It is shown that a structural factor affects the geometry of the state diagrams.     

Operando X-ray Absorption Spectroscopy Study of Pt/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> During the Total Oxidation of C<Subscript>3</Subscript>H<Subscript>6</Subscript>

Operando X-ray absorption fine structure (XAFS) investigations were performed on Pt/γ-Al₂O₃ during the total oxidation of C₃H₆ in reducing and oxidizing atmospheres. Study of the Pt valance state and catalytic conversion behavior as a function of temperature revealed that both the creation of metallic Pt sites and the activation of adsorbed species on Pt are important for the functioning of the catalytic reaction at low temperature.     

Structural analyses of RuO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>/Ti and IrO<Subscript>2</Subscript>–RuO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>/Ti anodes used in industrial chlor-alkali membrane processes

The morphology and composition of RuO₂–TiO₂/Ti and IrO₂–RuO₂–TiO₂/Ti anodes, which have been used for the production of chlorine for more than 10 years, were analyzed by various methods; such as high-resolution scanning electron microscopy, high-resolution Auger electron spectroscopy, electron probe X-ray emission microanalysis and X-ray diffraction analysis. Drastic changes in the surface morphology, including partial exfoliation of a small amount of the oxide layer and a reduction in the content of ruthenium species through dissolution, were observed for the RuO₂–TiO₂/Ti anode. For the IrO₂–RuO₂–TiO₂/Ti anode, on the other hand, there were moderate changes in the surface morphology and moderate dissolution of iridium and ruthenium species.     

Performance evaluation of a synthesized and characterized Pebax1657/PEG1000/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> membrane for CO<Subscript>2</Subscript>/CH<Subscript>4</Subscript> separation using response surface methodology

In this work, the response surface methodology (RSM) based on the central composite design (CCD) was used to examine effects of different gamma alumina (γ-Al₂O₃) loadings (0 to 8 wt.%) and various polyethylene glycol 1000 (PEG1000) contents (0 to 40 wt.%) as parameters on membrane preparation. Accordingly, pure carbon dioxide (CO₂) and methane (CH₄) gasses permeability and ideal CO₂/CH₄ selectivity values were considered as responses. Poly (ether block amide) 1657 (Pebax1657) was used as the base polymer matrix for the membranes fabrication. The neat Pebax1657 membrane was prepared via solution casting-solvent evaporation method and the other membranes were prepared via solution blending technique. Analysis of variance (ANOVA) was used to analyze the experiments statistically and the results indicated that the optimized amounts of γ-Al₂O₃ nanoparticles and PEG1000 in order to enhance both CO₂ permeability and ideal CO₂/CH₄ selectivity were 8 wt.% and 10 wt.%, respectively. Additionally, a comparison between the separation performance of the neat membrane, the nanocomposite membrane with the optimum amount of γ-Al₂O₃ nanoparticles, the blended membrane with optimum amounts of PEG1000, and the blended nanocomposite membrane with optimum amounts of γ-Al₂O₃ nanoparticles and PEG1000 was presented. The obtained gas permeation results showed that the blended nanocomposite membrane exhibits the highest CO₂/CH₄ separation performance compared to the neat Pebax membrane.     

Exploring the Redox Behavior of La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>Mn<Subscript>1−x</Subscript>Al<Subscript>x</Subscript>O<Subscript>3</Subscript> Perovskites for CO<Subscript>2</Subscript>-Splitting in Thermochemical Cycles

Mixed oxides with perovskite structure have been proposed as promising alternative for the solar fuel production via thermochemical redox cycles. For this work, the system La_0.6Sr_0.4Mn_1?xAl_xO₃ (x?=?0 to 0.8) was selected according to its high thermal stability and rapid oxidation kinetics, and the influence of the Al/Mn ratio on the redox properties was investigated. The characterization of the five oxides samples with different Al content confirmed the high redox capacity and the favorable behavior of these materials in consecutive cycles, as analyzed thermogravimetrically. The results show that following reduction at 1300?°C in inert atmosphere up to 0.32 mmol g^?1 of O₂ are released, while a 10-cycle reaction test confirms the feasibility of long term operation with these perovskites. It was observed that the reduction extent was enhanced with increasing the Al-content, but the oxidation degree is maximum for compositions near x?=?0.5, corresponding to an O₂ release of 0.318 mmol g^?1 (δ?=?0.132). After selecting the compositions with more promising redox properties, additional reactions were performed in a lab-scale fixed bed reactor with injection of CO₂ in the oxidation step at 900?°C in order to generate CO. In these tests, the most interesting results were obtained for the perovskite La_0.6Sr_0.4Mn_0.6Al_0.4O_3, with reduction extent of 0.266 mmol?g^?1, but the production of CO is in comparison significantly lower (0.114 mmol?g^?1). Further studies are required to determine the best operation conditions for thermochemical cycles using those materials.     

Photon interaction parameters for some ZnO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Some photon interaction parameters such as mass attenuation coefficient, effective atomic number, half value layer, mean free path and electron density for 15ZnO–(17.5–x)Al₂O₃–xFe₂O₃–67.5P₂O₅ glass system (x = 0, 7.5, 12.5, 17.5) and 15ZnO–(25–x)Al₂O₃–xFe₂O₃–60P₂O₅ glass system (x = 0, 25) have been investigated in the photon energy range of 1 keV to 100 GeV. It has been observed that all the photon interaction parameters for the selected glass systems vary with the photon energy. Among the selected glass systems, the sample 15ZnO–25Fe₂O₃–60P₂O₅ glass system shows maximum values for mass attenuation coefficients, effective atomic numbers, electron densities and minimum values for mean free path and half value layer in the entire energy grid.     

Structural heterogeneity of SiO<Subscript>2</Subscript>–Na<Subscript>2</Subscript>O–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> glass

It is shown that the phase heterogeneity of SiO₂–Na₂O–Al₂O₃ glass has a liquation and crystallization nature, the balance between which is determined by the conditions of their synthesis. An increase in the aluminum oxide content decreases the number of liquation and crystallization sites, and also the linear sizes of the crystalline formations without eliminating the phase separation due to the liquation. The area of metastable immiscibility in the SiO₂–Na₂O–Al₂O₃ system, which is determined by scanning electron microscopy, is probably wider than the area detected by the optical methods.